1. Field of the Invention
The present invention relates to a method for driving a head for a liquid-droplet jetting apparatus such as a head for an ink-jet printer, and a head for a liquid-droplet jetting apparatus such as a head for an ink-jet printer.
2. Description of the Related Art
In recent years, in an ink-jet printer which is a type of a liquid-droplet jetting apparatus, while there has been advancement in size reduction of a head, high densification of nozzles, and increasing a number of channels, a cost reduction has been facilitated.
With a reduction in size of the head, an area of an actuator which can be used per channel (in other words, one cavity which is one pressure chamber) tends to decrease. Whereas, there has been no change in a required size of an ink droplet, and a generation of a jetting pressure same as it has hitherto been used is sought in each channel. Therefore, as an existing situation, various ideas have been devised such as to have even slightly larger area of the actuator by reducing a width of a column between adjacent cavities (dimension in a row direction of the cavities), and to raise a drive voltage.
However, when the width of the column between the adjacent cavities is reduced, since a stiffness of the column is decreased, an effect of a cross-talk on the adjacent channels is increased. If the drive voltage is raised, a cost of parts for high voltage increases. Moreover, since an amount of heat generated is increased due to raising the drive voltage to be higher, it is necessary to lower a temperature. However, a design for lowering the temperature is difficult.
In view of the abovementioned circumstances, as it has been disclosed in U.S. Pat. No. 6,971,738 B2 and US Patent Application Publication No. 2006/0152556 A1 (corresponds to Japanese Patent Application Laid-open No. 2004-166463), there have been proposed a piezoelectric actuator, a liquid transporting apparatus, and an ink-jet head in which it is possible to impart a sufficient amount of deformation to a piezoelectric layer even when an area of a piezoelectric material arranged between the electrodes is decreased, and to prevent a deformation of a portion, of an actuator, corresponding to each of pressure chambers from affecting a portion corresponding to another pressure chamber.
However, in a piezoelectric actuator, a liquid transporting apparatus, and an ink-jet head described in U.S. Pat. No. 6,971,738 B2 and US Patent Application Publication No. 2006/0152556 A1, since a structure is such that for increasing an amount of deformation, a plurality of piezoelectric layers is stacked, and electrodes are provided between these stacked layers, the structure becomes complicated, and it is not sufficient from a point of lowering a drive voltage.